Patent Document 1 and the like propose an electronic key system using a key provided with an electronic key in control for locking/unlocking a vehicle and control for engine startup, performing control to unlock the vehicle and permitting engine startup when the electronic key stored in this key and inherent ID information of the vehicle equipment provided in the vehicle is corresponding, and performing control to lock the vehicle and not permit engine startup when an electronic key matching the inherent ID Information cannot be received.    Patent Document 1: Japanese Patent Publication (A) No. 2002-4675